I've started my Christmas cards this afternoon (Sunday).
When I started work back in the '60s protocol was important. A Minister of Religion was addressed as Reverend and Dear Sir unless he was higher up the ladder than a simple Reverend. And so it went on. We kept a Who's Who in the office and every honour etc was meticulously used. Even the order was important. I can still recall that I used to use J Graeme Bryson Esq CBE TD DL LLM JP as my guide for the different types of honour and their order of use. When I came to the Western Isles I discovered that formalities of address were virtually non-existent. In fact Lewis is a good training for New Zealand where first names are the order of the day most of the time and you have to know someone quite well to know their family or surname.
Nowadays however there are many more pitfalls for people who cling to some formality in addressing people on letters. I've given up trying to work out which of my female friends likes Ms, Miss, Mrs or just plain Jane Plain. Some use the family name from their first marriage, some revert to their surname, some use the surname of their second marriage, some hyphenate any combination of the two. All in all it's a bit of a minefield for the unknowing and the unwary.
Men are easier. I've taken to doing something I actually find anathema - or would have done until now - and for the most part am just using the forename and family/surname with no embellishments.
And that's just the start. I'm not venturing any further...